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    SubjectRe: Re: [RFC PATCH 1/6] virtio/console: Add splice_write support
    (2012/08/09 18:00), Amit Shah wrote:
    > On (Tue) 24 Jul 2012 [11:37:07], Yoshihiro YUNOMAE wrote:
    >> From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    >>
    >> Enable to use splice_write from pipe to virtio-console port.
    >> This steals pages from pipe and directly send it to host.
    >>
    >> Note that this may accelerate only the guest to host path.
    >>
    >> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    >> Cc: Amit Shah <amit.shah@redhat.com>
    >> Cc: Arnd Bergmann <arnd@arndb.de>
    >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >> ---
    >
    >> +/* Faster zero-copy write by splicing */
    >> +static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
    >> + struct file *filp, loff_t *ppos,
    >> + size_t len, unsigned int flags)
    >> +{
    >> + struct port *port = filp->private_data;
    >> + struct sg_list sgl;
    >> + ssize_t ret;
    >> + struct splice_desc sd = {
    >> + .total_len = len,
    >> + .flags = flags,
    >> + .pos = *ppos,
    >> + .u.data = &sgl,
    >> + };
    >> +
    >> + sgl.n = 0;
    >> + sgl.len = 0;
    >> + sgl.sg = kmalloc(sizeof(struct scatterlist) * MAX_SPLICE_PAGES,
    >> + GFP_ATOMIC);
    >
    > Do you expect this function to be called from interrupt context?

    No, not at all. Oops, that should be GFP_KERNEL...

    Thank you for pointing it out.

    --
    Masami HIRAMATSU
    Software Platform Research Dept. Linux Technology Center
    Hitachi, Ltd., Yokohama Research Laboratory
    E-mail: masami.hiramatsu.pt@hitachi.com




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